Document DE 199 59 276 A1 reveals a device and a test method for seat occupancy detection for vehicle seats as a prerequisite for intelligent restraint systems with personal classification and matched actuation strategy for belt tensioners, belt force limiters and airbags. This device has as basis a thin flexible supporting structure, e.g. a plastics film or a matrix of plastics strips, that is placed immediately below the entire seat area and closely adapts to the seat contour. Integrated in the supporting structure are a plurality of flat pressure sensors, one or more flat data storages, one or more flat transponders as well as an autonomous voltage source. The data pattern ascertained represents the kind and strength of the seat occupancy as well as the seat pressure profile.
Such a device is very expensive as already the required components are very expensive and moreover the installation on the seat foam or the seat cover is labor and cost intensive. Moreover, such a device is sensitive and prone to error.